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The purpose of this paper is to improve photoelectric detection target (PDT) optical detection performance and detection view, by analyzing its influence factors and putting forward a new method to design its optical detection system.

Using rectangle linked photoelectric detector, with low noise and high response, to design optical detection system and gain faint projectile image information; bringing forward a deviating focusing technique to eliminate detection blind area of photoelectric detector; and designing adjustable slit diaphragm to weaken background light influence.

The results of experimentation in shooting range show that the new PDT has improved detection sensitivity and performance.

The paper presents a new design method in photoelectric detection target (PDT) optical detection system, which can provide a new method to design fire across measurement system and gain accurate projectile's coordinates data in the shooting range.

Reducing production auxiliary time is the key to improve the efficiency of the existing mixed-flow assembly line. This paper proposes a method combining improved genetic algorithm (GA) and Flexsim software. It also investigates mixed-flow assembly line scheduling and just-in-time (JIT) parts feeding scheme to reduce waste in production while taking the existing hill-drop mixed-flow assembly line as an example to verify the effectiveness of the method.

In this research, a method is presented to optimize the efficiency of the present assembly line. The multi-objective mathematical model is established based on the objective function of the minimum production cycle and part consumption balance, and the solution model is developed using multi-objective GA to obtain the mixed flow scheduling scheme of the hill-drop planter. Furthermore, modeling and simulation with Flexsim software are investigated along with the contents of line inventory, parts transportation means, daily feeding times and time points.

Theoretical analysis and simulation experiments are carried out in this paper while taking an example of a hill-drop planter mixed-flow assembly line. The results indicate that the method can effectively reduce the idle and overload of the assembly line, use the transportation resources rationally and decrease the accumulation of the line inventory.

The method of combining improved GA and Flexsim software was used here for the first time intuitively and efficiently to study the balance of existing production lines and JIT feeding of parts. Investigating the production scheduling scheme provides a reference for the enterprise production line accompanied by the quantity allocation of transportation tools, the inventory consumption of the spare parts along the line and the utilization rate of each station to reduce the auxiliary time and apply practically.

The precise segmentation of brain tumors is the most important and crucial step in their diagnosis and treatment. Due to the presence of noise, uneven gray levels, blurred boundaries and edema around the brain tumor region, the brain tumor image has indistinct features in the tumor region, which pose a problem for diagnostics. The paper aims to discuss these issues.

In this paper, the authors propose an original solution for segmentation using Tamura Texture and ensemble Support Vector Machine (SVM) structure. In the proposed technique, 124 features of each voxel are extracted, including Tamura texture features and grayscale features. Then, these features are ranked using the SVM-Recursive Feature Elimination method, which is also adopted to optimize the parameters of the Radial Basis Function kernel of SVMs. Finally, the bagging random sampling method is utilized to construct the ensemble SVM classifier based on a weighted voting mechanism to classify the types of voxel.

The experiments are conducted over a sample data set to be called BraTS2015. The experiments demonstrate that Tamura texture is very useful in the segmentation of brain tumors, especially the feature of line-likeness. The superior performance of the proposed ensemble SVM classifier is demonstrated by comparison with single SVM classifiers as well as other methods.

The authors propose an original solution for segmentation using Tamura Texture and ensemble SVM structure.

This paper aims to analyze a failure case of a P110 tube in a CO₂ flooding well.

The chemical composition, microstructure and mechanical properties of the failed P110 tubing steel were tested, and met the API Spec 5CT standard. The fractures were investigated by scanning electron microscopy and energy dispersive spectroscopy.

Fracture was induced by stress corrosion cracking (SCC) and that the stress concentration caused by the mechanical damage played an important role in the failure. The failure case is a SCC failure affected by mechanical damage and galvanic corrosion.

The effect of the infiltration of groundwater was studied in the failure case. The stress concentration caused by the mechanical damage played an important role in the failure.

This paper aims to present the mechanical design and kinematics of a novel rigid-flexible coupling hybrid robot to develop a promising aeroengine blades in situ repair technology.

According to requirements analysis, a novel rigid-flexible coupling hybrid robot is proposed by combining a three degrees of freedom (DOF) parallel mechanism with a flexible continuum section. Then the kinematics models of both parallel mechanism and flexible continuum section are derived respectively. Finally, based on equivalent joint method, a two-step numerical iterative inverse kinematics algorithm is proposed for the whole robot: (1) the flexible continuum section is equivalently transformed to a 2-DOF spherical joint, thus the approximate analytical inverse kinematic solution can be obtained; (2) the accurate solution is derived by an iterative derivation of both parallel mechanism and flexible continuum section.

To verify structure scheme and the proposed kinematics modeling method, numerical simulations and prototype experiments are implemented. The results show that the proposed kinematics algorithm has sufficient accuracy and computational efficiency in the whole available workspace, that is end-effector position error and orientation error are less than 0.2 mm and 0.01° respectively, and computation time is less than 0.22s.

A novel rigid-flexible coupling hybrid robot for aeroengine blades in situ repair is designed. A two-step numerical iterative inverse kinematics algorithm is proposed for this unique hybrid robots, which has good accuracy and computational efficiency.

The purpose of this paper is to identify the determinants for currency internationalization and forecast the potential of RMB as an international reserve currency.

This paper performs linear or non-linear regressions of the shares of eight major international reserve currencies as the reserve assets in global central banks on the macro economic and financial variables of their corresponding countries to identify the determinants for their international positions, and conducts an “counter-factual simulation” for the potential of RMB as an international reserve currency.

This paper finds that the economic size and the “network externalities” are the most important determinants for the international status of a reserve currency; that exchange rate volatility has negative impacts; the conditions for the RMB internationalization are basically available. The simulation for the potential of RMB as an international reserve currency reveals that the international role of RMB could surpass that of the Japanese Yen and the British Pound, and get close to Euro in the coming 15 years. Based on the empirical evidence, this paper suggests a promoting strategy for RMB internationalization.

This paper has not taken the influence of economic systemic and political factors on the process of RMB internationalization into account.

RMB internationalization promotion should follow the strategy of “stably create RMB international demand in the initial period and dramatically release the RMB overseas supply in the latter period” in the coming 15 years.

The conclusions and policy implications are from the results of the empirical analysis on the 45-year historical experience on the eight main international currencies.

COVID-19 has severely affected urban and rural tourism in China, which has been extensively reported in the newspapers. This paper aims to discuss the impact of COVID-19 on urban and rural tourism at each critical juncture of the COVID-19 pandemic, as well as the studies, measures and attitudes of various stakeholders toward urban and rural tourism and their future development.

This paper collects Chinese news reports as the research object and uses ROST Content Mining 6.0 and Gephi software to analyze and visualize the data for high-frequency words and analyzed the discourse of stakeholders within the newspaper text.

This study found that prior to February 20, 2020, the Chinese Government mainly focused on pandemic prevention. From February 21 to April 3 (before The Qingming Festival), resumption of work and production became the theme. From April 4 to May 1 (before May Day), a time-sharing reservation system was widely implemented and the differentiation between urban and rural tourism became more prominent. After May 1, rural tourism attracted greater attention.

This paper uses discourse analysis to understand the impact of COVID-19 on urban and rural tourism from the perspective of time nodes and the relationship between various stakeholders and predicts the development trends within urban and rural tourism. This paper enriches and expands tourism management knowledge in the face of major crises, providing valuable advice for managers and investors and makes suggestions for the development of urban and rural tourism.

COVID-19已严重影响了中国的城市和乡村旅游业, 报纸上对此进行了广泛报道。本文旨在探讨在COVID-19大流行的每个关键时刻对城乡旅游的影响, 以及各种利益相关者对城乡旅游及其未来发展的观点, 措施和态度。

本文以中文新闻报道为研究对象, 利用ROST Content Mining 6.0和Gephi软件对高频词数据进行分析和可视化, 分析了报纸正文中利益相关者的话语。

这项研究发现, 在2020年2月20日之前, 中国政府主要将重点放在疫情防控上。 2月21日至4月3日（清明节之前）, 复工复产成为主题。 从4月4日至5月1日（五一节之前）, 分时预约系统得到广泛实施, 城市和乡村旅游业的区别更加突出。 5月1日之后, 乡村旅游引起了更多关注。

本文通过话语分析从时间节点和各个利益相关者之间的关系的角度了解了COVID-19对城乡旅游业的影响, 并预测了城乡旅游业的发展趋势。 面对重大危机, 本文丰富和扩展了旅游管理知识, 为管理者和投资者提供了宝贵的建议, 并为城乡旅游业的发展提供了建议。

COVID-19 ha afectado gravemente al turismo urbano y rural en China, que ha sido ampliamente informado en los periódicos. Este documento tiene como objetivo discutir el impacto de COVID-19 en el turismo urbano y rural en cada coyuntura crítica de la pandemia de COVID-19, así como los puntos de vista, las medidas y las actitudes de diversos interesados en relación con el turismo urbano y rural y su desarrollo futuro.

Este documento recopiló informes de noticias chinos como objeto de investigación y utilizó el software ROST Content Mining 6.0 y Gephi para analizar y visualizar los datos de palabras de alta frecuencia y analizó el discurso de los interesados dentro del texto del periódico.

Este estudio encontró que antes del 20 de febrero de 2020, el gobierno chino se centró principalmente en la prevención de la pandemia en lugares pintorescos. Del 21 de febrero al 3 de abril (antes del Festival de Qingming), la reanudación del trabajo y la producción se convirtió en el tema. Desde el 4 de abril hasta el 1 de mayo (antes del Primero de Mayo), se implementó ampliamente un sistema de reserva de tiempo compartido y la diferenciación entre el turismo urbano y el rural se hizo más prominente. Después del 1 de mayo, el turismo rural atrajo mayor atención.

En este documento, se utiliza el análisis del discurso para comprender el impacto de COVID-19 en el turismo urbano y rural desde la perspectiva de los nodos de tiempo y la relación entre los diversos interesados y se predice las tendencias de desarrollo dentro del turismo urbano y rural. Este trabajo enriquece y amplía el conocimiento de la gestión turística frente a las grandes crisis, brindando valiosos consejos a administradores e inversores, y hace sugerencias para el desarrollo del turismo urbano y rural.

The purpose of this paper is to investigate the pricing strategy and the impact of agents' risk preference in a dual-channel supply chain in which both agents are risk-averse.

The authors make use of the mean-variance (MV) method to measure the risk aversion of the agents and apply Stackelberg game to obtain the optimal strategies of the proposed models. Furthermore, the authors compare the optimal strategies with that in the benchmark model in which no agent is risk-averse.

The authors find that the pricing decisions can be divided into four categories according to the risk attitudes of the agents: the decisions that are independent of two agents' risk attitudes, the decisions that depend on only one agent’s risk attitude (i.e. depend on only manufacturer's risk attitude and depend on only retailer's risk attitude) and the decisions that depend on both agents' risk attitudes. In addition, the authors find that the retail price will be lower and the wholesale price in most cases will be lower than that in the benchmark when at least one agent's risk control is effective; the demand will be always increasing as long as one agent's risk control is effective. Furthermore, compared to the benchmark, a win-win strategy (i.e. Pareto improvement) for the supply chain members can be obtained in a certain range where the agents' risk controls are appropriate.

This research provides a theoretical reference for the managers to make the pricing decisions and the risk control in dual-channel supply chains with heterogeneous preference consumers.

The model for digitally controlled three-phase pulse width modulation (PWM) boost rectifiers is a sampled data model, which is different from the continuous time domain models presented in previous studies. The controller, which is tuned according to the model in continuous time domain and discretized by approximation methods, may exhibit some unpredictable performances and even result in unstable systems under some extreme situations. Consequently, a small-signal discrete-time model of digitally controlled three-phase PWM boost rectifier is required. The purpose of this paper is to provide a simple but accurate small-signal discrete-time model of digital controlled three-phase PWM boost rectifier, which explains the effect of the sampling period, modulator and time delays on system dynamic and improves the control performance.

Based on the Laplace domain analysis and the waveforms of up-down-count modulator, the small signal model of digital pulse width modulation (DPWM) in the Laplace domain is presented. With a combination of state-space average and a discrete-time modeling technique, a simplified large signal discrete time model is developed. With rotation transformation and feed-forward decoupling, the large-signal model is decoupled into a single input single output system with rotation transformation. Then, an integrated small signal model in the Laplace domain is constructed that included the time delay and modulation effect. Implementing the modified z-transform, a small-signal discrete-time model is derived from the integrated small signal model.

In a digital control system, besides the circuit parameters, the location of pole of open-loop transfer function is also related to system sampling time, affecting the system stability, and the time delay determines the location of the zero of open-loop transfer function, affecting the system dynamic. In addition to the circuit parameters discussed in previous literature, the right half plane (RHP) zero is also determined by the sampling period and the time delay. Furthermore, the corner frequency of the RHP zero is mainly determined by the sampling period.

The model developed in this paper, accounting for the effect of the sampling period, modulator and time delays on the system dynamic, give a sufficient insight into the behavior of the digitally controlled three-phase PWM rectifier. It can also explain the effect of sampling period and control delay time on system dynamic, accurately predict the system stability boundary and determine the oscillation frequency of the current loop in critical stable. The experimental results verify that the model is a simple and accurate control-oriented small-signal discrete-time model for the digitally controlled three-phase PWM boost rectifier.

The purpose of this paper was to study the relationship between safe storage life and storage mode of hot-rolled sheet (Q235, X70) in humid environment, and a prediction model of safe storage life under different storage modes was established.

The corrosion behavior of hot-rolled sheets under different storage conditions was studied with immersion experiment and morphology observation.

The results show that pitting occurs on the hot-rolled sheets in humid environment, and the corrosion behavior is strongly related with the storage mode. When they are stored separately, the number and depth of pits first increase and then decrease as the Cl⁻ concentration rises, while for the stack storage, pit depth increases with increasing Cl⁻ concentration. The safe storage time of separate storage is longer than that of stack storage. Based on this, a model of chloride ion concentration and storage life was established.

A storage safe life model of hot-rolled sheet in humid environment is proposed.